v4l2: improve capturing for davinci vpfe driver

- Add option to disable VIDEO_DQBUF workaround for certein capture cards.
- Add workaround for davinci vpfe driver that reports wrong bytesused value

modules/access/v4l2.c

@@ -99,6 +99,11 @@ static void AccessClose( vlc_object_t * );
     "Force usage of the libv4l2 wrapper." )
 #endif
 
+#define DQBUF_TEXT N_("Workaround v4l2 driver bug (default on)")
+#define DQBUF_LONGTEXT N_( \
+    "Workaround a driver bug by dequeuing the requested buffers before closing." \
+    "The bug manifests iteslf by hanging or crashing upon closing of v4l2 device.")
+
 #define CTRL_RESET_TEXT N_( "Reset v4l2 controls" )
 #define CTRL_RESET_LONGTEXT N_( \
     "Reset controls to defaults provided by the v4l2 driver." )
@@ -289,6 +294,7 @@ vlc_module_begin ()
 #ifdef HAVE_LIBV4L2
     add_bool( CFG_PREFIX "use-libv4l2", false, NULL, LIBV4L2_TEXT, LIBV4L2_LONGTEXT, true );
 #endif
+    add_bool( CFG_PREFIX "workaround-dqbuf", true, NULL, DQBUF_TEXT, DQBUF_LONGTEXT, true );
 
     set_section( N_( "Tuner" ), NULL )
     add_integer( CFG_PREFIX "tuner", 0, NULL, TUNER_TEXT, TUNER_LONGTEXT,
@@ -550,6 +556,7 @@ struct demux_sys_t
 
     int i_width;
     int i_height;
+    int i_pitch;
     float f_fps;            /* <= 0.0 mean to grab at full rate */
     mtime_t i_video_pts;    /* only used when f_fps > 0 */
     int i_fourcc;
@@ -564,7 +571,6 @@ struct demux_sys_t
     /* Controls */
     char *psz_set_ctrls;
 
-
 #ifdef HAVE_LIBV4L2
     /* */
     int (*pf_close)( int );
@@ -575,6 +581,8 @@ struct demux_sys_t
     int (*pf_munmap)( void *, size_t );
     bool b_libv4l2;
 #endif
+    /* V4L2 driver bug workaround */
+    bool b_workaround_dqbuf;
 };
 
 #ifdef HAVE_LIBV4L2
@@ -690,6 +698,8 @@ static void GetV4L2Params( demux_sys_t *p_sys, vlc_object_t *p_obj )
     p_sys->i_selected_standard_id =
         i_standards_list[var_CreateGetInteger( p_obj, "v4l2-standard" )];
 
+    p_sys->b_workaround_dqbuf = var_CreateGetBool( p_obj, "v4l2-workaround-dqbuf" );
+
     p_sys->i_selected_input = var_CreateGetInteger( p_obj, "v4l2-input" );
     p_sys->i_selected_audio_input =
         var_CreateGetInteger( p_obj, "v4l2-audio-input" );
@@ -983,7 +993,6 @@ static void DemuxClose( vlc_object_t *p_this )
 {
     struct v4l2_buffer buf;
     enum v4l2_buf_type buf_type;
-    unsigned int i;
 
     demux_t     *p_demux = (demux_t *)p_this;
     demux_sys_t *p_sys   = p_demux->p_sys;
@@ -1000,20 +1009,24 @@ static void DemuxClose( vlc_object_t *p_this )
         case IO_METHOD_MMAP:
         case IO_METHOD_USERPTR:
             /* Some drivers 'hang' internally if this is not done before streamoff */
-            for( unsigned int i = 0; i < p_sys->i_nbuffers; i++ )
+            if( p_sys->b_workaround_dqbuf )
             {
-                memset( &buf, 0, sizeof(buf) );
-                buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-                buf.memory = ( p_sys->io == IO_METHOD_USERPTR ) ?
-                    V4L2_MEMORY_USERPTR : V4L2_MEMORY_MMAP;
-                v4l2_ioctl( p_sys->i_fd, VIDIOC_DQBUF, &buf ); /* ignore result */
+                for( unsigned int i = 0; i < p_sys->i_nbuffers; i++ )
+                {
+                    memset( &buf, 0, sizeof(buf) );
+                    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+                    buf.memory = ( p_sys->io == IO_METHOD_USERPTR ) ?
+                        V4L2_MEMORY_USERPTR : V4L2_MEMORY_MMAP;
+                    if( v4l2_ioctl( p_sys->i_fd, VIDIOC_DQBUF, &buf ) < 0 ) {
+                        msg_Err( p_this, "VIDIOC_DQBUF %d/%d failed", i, p_sys->i_nbuffers );
+                    }
+                }
             }
 
             buf_type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
             if( v4l2_ioctl( p_sys->i_fd, VIDIOC_STREAMOFF, &buf_type ) < 0 ) {
                 msg_Err( p_this, "VIDIOC_STREAMOFF failed" );
             }
-
             break;
         }
     }
@@ -1027,7 +1040,7 @@ static void DemuxClose( vlc_object_t *p_this )
             break;
 
         case IO_METHOD_MMAP:
-            for( i = 0; i < p_sys->i_nbuffers; ++i )
+            for( unsigned int i = 0; i < p_sys->i_nbuffers; ++i )
             {
                 if( v4l2_munmap( p_sys->p_buffers[i].start, p_sys->p_buffers[i].length ) )
                 {
@@ -1037,7 +1050,7 @@ static void DemuxClose( vlc_object_t *p_this )
             break;
 
         case IO_METHOD_USERPTR:
-            for( i = 0; i < p_sys->i_nbuffers; ++i )
+            for( unsigned int i = 0; i < p_sys->i_nbuffers; ++i )
             {
                free( p_sys->p_buffers[i].start );
             }
@@ -1342,7 +1355,14 @@ static block_t* GrabVideo( demux_t *p_demux )
             return 0;
         }
 
-        p_block = ProcessVideoFrame( p_demux, p_sys->p_buffers[buf.index].start, buf.bytesused );
+//         msg_Err( p_demux, "New frame has size: %d (%d) %d",
+//                  buf.bytesused, p_sys->i_pitch * p_sys->i_height, buf.length );
+        p_block = ProcessVideoFrame( p_demux, p_sys->p_buffers[buf.index].start,
+#if 0
+                                     buf.bytesused );
+#else
+                                     p_sys->i_pitch * p_sys->i_height );
+#endif
         if( !p_block ) return 0;
 
         /* Unlock */
@@ -2098,6 +2118,8 @@ static int OpenVideoDev( vlc_object_t *p_obj, demux_sys_t *p_sys, bool b_demux )
     if( fmt.fmt.pix.sizeimage < i_min )
         fmt.fmt.pix.sizeimage = i_min;
 
+    p_sys->i_pitch = fmt.fmt.pix.bytesperline;
+
 #ifdef VIDIOC_ENUM_FRAMEINTERVALS
     /* This is new in Linux 2.6.19 */
     /* List supported frame rates */